The present disclosure relates to a device, a method of manufacturing a device, a board, a method of manufacturing a board, a mounting structure, a mounting method, an LED display, an LED backlight and an electronic device.
In related arts, as a method of electrically connecting wiring formed on a board and a device to each other, there are various methods such as solder bonding, bonding by compression, connection using a conductive paste, bonding using a non-conductive paste and the like; however, they have the following disadvantages.
In solder bonding, for example, it is necessary to increase the temperature of solder to a solder melting temperature of approximately 250° C. to 300° C., so it is necessary for a device and a board to have heat resistance to the temperature. Moreover, because of a difficulty in forming a fine solder bump, the spread of the melted solder, or the like, for example, it is difficult to achieve a wiring connection with a narrow pitch of approximately 30 μm.
In bonding by compression, typically, a newly-formed surface of the bump and a newly-formed surface of the wiring are contacted with each other and bonded together by applying both of pressure and ultrasonic vibration to a joint surface. However, for example, in the case where the size of a chip is as large as approximately 30 mm×30 mm, it is difficult to uniformly apply ultrasonic vibration, thereby it is difficult to achieve a multi-pin connection. Further, for example, in the case where the bump is as small as approximately 10 μm×10 μm, the connection principle does not work with ultrasonic waves with an amplitude of approximately 20 μm, so it is difficult to form a fine bump.
In connection using a conductive paste, typically, conductivity is developed by a conductive filler, so connection using a conductive paste is applicable only to the connection between bumps or wirings which are sufficiently larger than the size of the filler. A typical conductive filler such as carbon or silver has a diameter of approximately 1 μm at the minimum; however, such a conductive filler has a particle size distribution, and, for example, particles with a diameter of approximately 50 μm are mixed in the filler. Therefore, connection using a conductive paste is not suitable for the connection of a bump or wiring with a size of, for example, 100 μm or less. Moreover, typically, the conductive paste has poor adhesion, so it is difficult to obtain a highly reliable connection.
Bonding using a non-conductive paste is suitable to form a fine bump; however, it is difficult to ensure the reliability against a stress such as a thermal cycle.
As a technique of achieving a fine multi-pin connection which is difficult to achieve in the above related arts, a connection technique using an anisotropic conductive film (ACF) in which conductive particles with a diameter of approximately 5 μm are diffused into a thermoset film has been developed (for example, refer to Japanese Unexamined Patent Application Publication No. 2005-144745), and as of now, the connection of approximately 1000 pins with a pitch of approximately 30 μm is achieved.
However, in the connection technique using the above-described anisotropic conductive film, the capture rate of conductive particles by bumps finely formed is reduced, or it is difficult to absorb variations in heights of bumps in the case where conductive particles become smaller, so there are a large number of issues which need to be resolved to form finer bumps and increase the number of pins.
In view of the foregoing, it is desirable to provide a mounting structure and a mounting method which are capable of securely electrically connecting wiring on a board and a device to each other in the case where the device is mounted on the board, and are capable of forming a finer bump, and increasing the number of pins.
Moreover, it is desirable to provide a device and a board suitably applied to the above-described mounting structure and the above-described mounting method, and methods of manufacturing the device and the board.
Further, it is desirable to provide an LED display, an LED backlight and an electronic device on the basis of the above-described mounting structure.